//exists方法用来判断给定路径是否存在，然后不管结果如何，都会调用回调函数。
var fs = require('fs');
var process = require('process');
console.log('path:'+process.cwd());
//只能是目录
fs.exists('../app', function (exists) {
    console.log(exists);
    console.log(exists ? "it's there" : "no file!");
});